week 11 xray Flashcards
bergonie and tribondeau
metabolism, maturation and differention will govern which cells are more or less radiosensitive
physical factor of linear transfer function
the rate at which energy is transfered through the matter it is going through and it loses energy
units of linear energy transfer
keV/micrometer
how much energy is being loss per unit distance is defined as
linear energy transfer function
REB stands for
Relative biological effectiveness
REB is expressed in terms of?
comparison between a “standard” radiation type and some other type of ionizing radiation
fractionation is defined as?
breaking the total dose into smaller individual doses separated in time.
radio sensitivity physical factors?
fractionation
LET
Protraction
Protraction is defined as?
the total dose is continuously administered over an extended the time period
Both fractionation and protraction can reduce the biological effects of ionizing radiation- why?
Because cells can repair radiation damage
early effects of radiation
Effect manifests within minutes to days of exposure
Late =
Effect manifests in months to years
biologic effect:
oxygen effect and age
Radiosensitizing and radioprotective agents have been identified
Radiosensitizing agents
Oxygen effect
Increased oxygenation increases radiosensitivity of tissues
Oxygen effect is LET dependent- there is more oxygenation effect for low LET radiation.
Age biological effects
Sensitivity is greatest in utero birth and decreases until age 30; levels off and increases again in advanced age
dose response relationships
how much radiation vs how much response was observed
how can a dose response relationship be described as
linear vs non-linear
threshold vs nonthreshold relationship is used to describe what about the dose response relationship
place where something starts at a particular set of dose and the nonthreshold is a a response when any amount of dose is given
ambient level of response
means level of response present without or prior to any intervention
will a curve that goes in to the ambient level be easy to see or hard to see?
hard
the government uses radiation safety guidelines and estimating the biological effects of radiation
a linear, non-threshold dose-response model is used.
most important macromolecule for radiation exposure?
DNA
3 main radiation effects on macromolecules
breaking of main chain
crosslinking
point linking
Cross-linking
defined as?
Formation of new chemical bonds that link side-chains with one another
crosslinking results in
Results in increased viscosity of a macromolecular solution
point lesion is defined as?
Disruption or alteration of single chemical bonds
Changes in the cell may be undetectable to the repair mechanisms of the intracellular environment.
DNA and irradiation- 3 effects
Cell death
Malignant disease
Genetic damage
Most likely molecule to interact with a photon is ____?
water
Free radicals are
uncharged, highly reactive molecules or atoms with a single electron in their outer valence orbital.
____________ also result from combination of free radicals- this is an important component of radiation cell damage
Toxic substances
is it the indirect or the direct mechanism that has an effect on humans?
indirect
ALARA?
as little as reasonably possible
All ______ effects, and most normal tissue _____effects are deterministic.
early, late
Deterministic effects are characterized by
A threshold dose below which no effect is seen
Worsening of the effect as dose increases over the threshold
Stochastic effects account for the remaining _____ effects
late
does stochastic effects have a threshold for dose?
no
is the severity of the effects of radiation dose related?
no
Stochastic effects include
radiation carcinogenesis and hereditary effects.
Stochastic Effects expressed as?
statistically/ likelyhoods
early effects of radiation
Acute Radiation Syndrome
Local tissue damage
Cytogenetic damage
Acute Radiation Syndrome
Hematologic effects
Gastrointestinal effects
Central Nervous system effects
Local tissue damage
Skin
Gonads
Extremities
Cytogenetic damage
Observable with DNA analysis
Late Effects
Leukemia
Other malignant disease
Local tissue damage
Decreased life span
Genetic Damage
In utero radiation effects
Prenatal death
Neonatal death
Congenital malformation
Childhood malignancy
Decreased growth and developmento
early effects general consept of body area and radiation intensity?
For a given level of radiation intensity, the larger the body area exposed, the greater the effect
prodromal syndrome and a latent period is seen in
acute radiation syndrome.. which signifies that more symptoms are coming
Prodromal period/ Prodromal syndrome
occurs at doses
> 100 rads whole body
s/s of Prodromal period/ Prodromal syndrome
diarrhea, nausea, vomiting, Leucopenia
Followed quickly by manifest ARS if dose is high
Latent period may follow the prodrome
A period of relative recovery from prodromal symptoms
May last from hours to weeks
blood count changes as what rem?
50
vomitng occurs at twhat rem?
100
mortality dose
150 rem
LD
320-360
100% mortality
800 rem
the LD 50/60 is defined as
the dose at thiwch 50% the exposed pop. will die within 60 days
for human beings the LD 50/60 is estimated at_____ rads whole body exposure
350
early effects on local tissue
Erythema
Epilation
Desquamation
what can happen to the reproductive organs of male around 10 rads
sterility
at what level is sterility is temporary?
200
at what level is sterility is permenant?
500 rads
